So, if someone looks at, say, "cldr/nls/de/gregorian.js" where that format happens to be defined, and then tries to use that format in an application, they would likely find the value missing for some other locale potentially producing an error in application code.

While this specific discrepancy could be resolved by adding a default for that format, it points to a possible larger issue in maintaining the i18n code. To detect more such discrepancies, it would be good to have a tool that loads all the i18n files for gregorian (or other i18n "dojo/cldr/nls/" modules) and detects such discrepancies and reports on them -- if such a tool does not exist already?